How far must you stretch a spring with k = 1600 N/m to store 260 J of energy?

Energy stored in a spring = 1/2*k*x^2

Where, x = increase in length of the spring

Therefore,

260 = 1/2*1600*x^2 = 800x^2 = > x^2 = 260/800 = 0.325 = > x = sqrt (0.325) = 0.57 m

The length of the spring must increase by 0.57 m to store 260 J